Method for extracting fulvic acid molecules

Abstract

Methods for extracting molecules of fulvic acid from a humus material such as oxidized lignite are disclosed. The humus material is mixed with water to solubilize at least some of the fulvic acid molecules. A first filtration apparatus (which may be an ultrafiltration apparatus) may be used to separate at least some of the solubilized fulvic acid molecules from the humin and at least some of the humic acid molecules. A second filtration apparatus (which may be an ultrafiltration apparatus or a nanfiltration apparatus) may be used to then separate the fulvic acid molecules from most of the water and any remaining impurities. A digestion step may also be carried out where microorganisms are brought into contact with the mixture in the presence of oxygen in order to oxidize any unoxidized organic compounds in the humus material. Iron and aluminum may be precipitated and removed by the addition of a phosphate to improve the purity of the end-product.

1. A method for extracting molecules of fulvic acid from a humus material comprising molecules of humin, humic acid and fulvic acid, the method comprising the steps of: (a) mixing the humus material with water to solubilize at least some of the molecules of fulvic acid; and (b) separating at least some of the solubilized fulvic acid molecules from the humin molecules and from at least some of the humic acid molecules by ultrafiltration, and further comprising, between steps (a) and (b), a digestion step comprising contacting microorganisms with the mixture in the presence of oxygen to oxidize any unoxidized organic compounds in the humus material. 
     
     
       2. The method according to  claim 1  wherein the microorganisms are bacteria, protozoa, fungi or a mixture of two or more members selected from the group consisting of bacteria, protozoa and fungi. 
     
     
       3. The method according to  claim 1  wherein the microorganisms are contacted with the mixture by adding compost, compost tea, soil or manure to the mixture, the compost, compost tea, soil or manure comprising the microorganisms. 
     
     
       4. The method according to  claim 1  wherein air is bubbled through the mixture during the digestion step. 
     
     
       5. The method according to  claim 1  wherein at least some of the solubilized fulvic acid molecules are separated from at least some of the humic acid molecules by filtering the mixture through a first filtration apparatus which retains at least some of the humic acid molecules while allowing at least some of the solubilized fulvic acid molecules to pass through, wherein at least some of the solubilized fulvic acid molecules are separated from the humin molecules before or during filtering the mixture through said first filtration apparatus, wherein the first filtration apparatus is an ultrafiltration apparatus. 
     
     
       6. The method according to  claim 5  wherein the first filtration apparatus retains particles or compounds having a molecular weight of about 2500 to 12,500 Daltons. 
     
     
       7. The method according to  claim 6  wherein the first filtration apparatus retains particles or compounds having a molecular weight of at least about 8000 Daltons. 
     
     
       8. The method according to  claim 5  further comprising, after step (b), the step of (c) separating at least some of the solubilized fulvic acid molecules from part of the water by ultrafiltration or nanofiltration. 
     
     
       9. The method according to  claim 8  wherein step (c) further comprises separating at least some of the solubilized fulvic acid molecules from any salts in the mixture by ultrafiltration or nanofiltration. 
     
     
       10. The method according to  claim 8  wherein step (c) is carried out by filtering the mixture through a second filtration apparatus after being filtered through the first filtration apparatus, wherein the second filtration apparatus retains at least some of the solubilized fulvic acid molecules while allowing part of the water to pass through, wherein the second filtration apparatus is an ultrafiltration apparatus or a nanofiltration apparatus. 
     
     
       11. The method according to  claim 9  wherein step (c) is carried out by filtering the mixture through a second filtration apparatus after being filtered through the first filtration apparatus, wherein the second filtration apparatus retains at least some of the solubilized fulvic acid molecules while allowing part of the water and any salts in the mixture to pass through, wherein the second filtration apparatus is an ultrafiltration apparatus or a nanofiltration apparatus. 
     
     
       12. The method according to  claim 10  wherein the second filtration apparatus retains all or substantially all of the fulvic acid molecules which have passed through the first filtration apparatus. 
     
     
       13. The method according to  claim 10  wherein the second filtration apparatus retains particles or molecules having a molecular weight of about 250 to 1000 Daltons. 
     
     
       14. The method according to  claim 13  wherein the second filtration apparatus retains particles or molecules having a molecular weight of at least about 600 Daltons. 
     
     
       15. The method according to  claim 10  wherein the second filtration apparatus retains part of the water, thereby leaving the separated fulvic acid molecules from step (c) in a solution. 
     
     
       16. The method according to  claim 15  further comprising the step of reducing the water content of the solution obtained from step (c) to concentrate the solution. 
     
     
       17. The method according to  claim 15  further comprising the step of drying the solution obtained from step (c) to leave the fulvic acid in a powder. 
     
     
       18. The method according to  claim 5  wherein the first filtration apparatus allows all or substantially all of the solubilized fulvic acid molecules to pass through. 
     
     
       19. The method according to  claim 10  wherein the mixture is filtered through a third filtration apparatus before being filtered through the first filtration apparatus, wherein the third filtration apparatus retains the humin molecules and at least some of the humic acid molecules while allowing the solubilized fulvic acid molecules and at least some of the humic acid molecules to pass through, wherein the third filtration apparatus is an ultrafiltration apparatus. 
     
     
       20. The method according to  claim 19  wherein the third filtration apparatus retains particles or molecules having a molecular weight of more than about 12,500 Daltons. 
     
     
       21. The method according to  claim 20  wherein the third filtration apparatus retains particles or molecules having a molecular weight of at least about 25,000 Daltons. 
     
     
       22. The method according to  claim 18  wherein the first filtration apparatus retains all or substantially all of the humic acid molecules. 
     
     
       23. The method according to  claim 19  wherein all or substantially all of the humic acid molecules are retained by one or both of the first filtration apparatus and the third filtration apparatus. 
     
     
       24. The method according to  claim 5  further comprising, after step (a) but before filtering the mixture through the first filtration apparatus, the steps of adjusting the pH of the mixture to about 5 to 8, adding a phosphate to the mixture to precipitate any iron and any aluminum in the humus material as iron phosphate and aluminum phosphate and separating any precipitated iron phosphate and aluminum phosphate from the fulvic acid molecules. 
     
     
       25. The method according to  claim 24  wherein the phosphate is selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate, magnesium phosphate, calcium phosphate, and mixtures of two or more members selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate and calcium phosphate. 
     
     
       26. The method according to  claim 24  wherein the phosphate is phosphoric acid. 
     
     
       27. The method according to  claim 24  wherein the addition of the phosphate to the mixture is sufficient to adjust the pH of the mixture to about 5 to 8. 
     
     
       28. The method according to  claim 24  wherein an acid is added to the mixture to adjust the pH of the mixture to about 5 to 8. 
     
     
       29. The method according to  claim 28  wherein the acid is selected from the group consisting of phosphoric acid, acetic acid, citric acid, hydrochloric acid and sulfuric acid and mixtures of two or more members selected from the group consisting of phosphoric acid, acetic acid, citric acid, hydrochloric acid and sulfuric acid. 
     
     
       30. The method according to  claim 24  wherein an alkali is added to the mixture to adjust the pH of the mixture to about 5 to 8. 
     
     
       31. The method according to  claim 30  wherein the alkali is selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium carbonate, calcium-magnesium carbonate, potassium hydroxide and sodium hydroxide and mixtures of two or more members selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate, magnesium phosphate, calcium phosphate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium carbonate, calcium-magnesium carbonate, potassium hydroxide and sodium hydroxide. 
     
     
       32. The method according to  claim 19  further comprising, after filtering the mixture through the third filtration apparatus and before filtering through the first filtration apparatus, the steps of adjusting the pH of the mixture to about 5 to 8, adding a phosphate to the mixture to precipitate any iron and any aluminum in the humus material as iron phosphate and aluminum phosphate and separating any precipitated iron phosphate and aluminum phosphate from the fulvic acid molecules. 
     
     
       33. The method according to  claim 32  wherein the phosphate is selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate, magnesium phosphate, calcium phosphate, and mixtures of two or more members selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate and calcium phosphate. 
     
     
       34. The method according to  claim 32  wherein the phosphate is phosphoric acid. 
     
     
       35. The method according to  claim 32  wherein the pH of the mixture is adjusted to at least about 9.4 prior to filtering the mixture through the third filtration apparatus and wherein the pH of the mixture is adjusted, by the addition of an acid, to about 5 to 8 after filtering the mixture through the third filtration apparatus. 
     
     
       36. The method according to  claim 35  wherein the acid is selected from the group consisting of phosphoric acid, acetic acid, citric acid, hydrochloric acid and sulfuric acid and mixtures of two or more members selected from the group consisting of phosphoric acid, acetic acid, citric acid, hydrochloric acid and sulfuric acid. 
     
     
       37. The method according to  claim 35  wherein the pH of the mixture is adjusted to at least about 9.4 by the addition of an alkali. 
     
     
       38. The method according to  claim 37  wherein the alkali is selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium carbonate, calcium-magnesium carbonate, potassium hydroxide and sodium hydroxide and mixtures of two or more members selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium pyrophosphate, magnesium phosphate, calcium phosphate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium carbonate, calcium-magnesium carbonate, potassium hydroxide and sodium hydroxide. 
     
     
       39. The method according to  claim 1  wherein the humus material comprises one or more members selected from the group consisting of peats, oxidized lignites, peat moss, composts, brown coals, soil, pond sediment and biosolids. 
     
     
       40. The method according to  claim 39  wherein the humus material comprises oxidized lignite, and wherein the oxidized lignite is leonardite. 
     
     
       41. The method according to  claim 1  wherein the humus material is ground prior to being mixed with the water in step (a). 
     
     
       42. The method according to  claim 1  wherein the mixture in step (a) comprises from about 3% to about 35% by weight of the humus material. 
     
     
       43. The method according to  claim 1  further comprising the step of heating the mixture prior to step (b). 
     
     
       44. The method according to  claim 43  wherein the mixture is heated at a temperature from about 50° C. to 70° C. 
     
     
       45. The method according to  claim 1  further comprising allowing the mixture to settle prior to step (b). 
     
     
       46. The method according to  claim 5  further comprising the step of filtering the mixture to remove particles of a chosen size prior to filtering the mixture through the first filtration apparatus. 
     
     
       47. The method according to  claim 1  wherein the water in step (a) is provided in an aqueous solution which is mixed with the humus material. 
     
     
       48. A method for producing an agricultural or horticultural solution comprising fulvic acid molecules, the method comprising:
 (a) mixing a humus material comprising molecules of humin, humic acid and fulvic acid with water to solubilize at least some of the fulvic acid molecules; 
 (b) filtering the mixture through a first filtration apparatus which is configured to retain particles or molecules having a molecular weight of 2500 to 12,500 Daltons to separate at least some of the fulvic acid molecules from at least some of the humic acid molecules, the humin molecules being separated from the fulvic acid molecules prior to or during filtering the mixture through the first filtration apparatus; and 
 (c) passing the filtrate from the first filtration apparatus through a second filtration apparatus, wherein the second filtration apparatus retains at least some of the solubilized fulvic acid molecules and some of the water, thereby producing the solution, and 
 
       further comprising, between steps (a) and (b), a digestion step comprising contacting microorganisms with the mixture in the presence of oxygen to oxidize any unoxidized organic compounds in the humus material. 
     
     
       49. The method according to  claim 48  wherein the second filtration apparatus is configured to retain particles or molecules having a molecular weight of about 250 to 1000 Daltons. 
     
     
       50. The method according to  claim 49  wherein the mixture is filtered through a third filtration apparatus prior to being filtered through the first filtration apparatus, the third filtration apparatus retaining the humin molecules and at least some of the humic acid molecules while allowing the solubilized fulvic acid molecules to pass through, wherein the third filtration apparatus is configured to retain particles or molecules having a molecular weight of more than about 12,500 Daltons. 
     
     
       51. The method according to  claim 50  further comprising, after filtering the mixture through the third filtration apparatus and before filtering the mixture through the first filtration apparatus, the steps of adjusting the pH of the mixture to about 5 to 8, adding a phosphate to the mixture to precipitate any iron and any aluminum in the humus material as iron phosphate and aluminum phosphate and separating any precipitated iron phosphate and aluminum phosphate from the fulvic acid molecules. 
     
     
       52. A method for extracting molecules of fulvic acid from a humus material comprising molecules of humin, humic acid and fulvic acid, the method comprising the steps of:
 (a) mixing ground humus material with water to solubilize at least some of the fulvic acid molecules; 
 (b) contacting microorganisms with the mixture in the presence of oxygen for a period of 1 to 7 days to oxidize any unoxidized organic compounds in the humus material; 
 (c) adding a phosphate to the mixture and adjusting the pH of the mixture to about 5 to 8 to precipitate any iron and any aluminum in the humus material as iron phosphate and aluminum phosphate, wherein any precipitated iron phosphate and aluminum phosphate is removed in one or more of steps (d), (g) and (h); 
 (d) passing the mixture through a first filter, the pores of the first filter being sized to retain particles have a size of at least 74 microns, the filtrate from the first filter comprising a mixture of a solution comprising fulvic acid molecules and solids having sizes smaller than about 74 microns; 
 (e) allowing the filtrate from the first filter to settle for a period of time; 
 (f) heating the filtrate from the first filter at temperature from about 50° C. to 70° C.; 
 (g) passing the filtrate from the first filter through a second filter, the pores of the second filter being sized to retain particles having a size of about 5 to 30 microns, the filtrate from the second filter comprising a mixture of a solution comprising the solubilized fulvic acid molecules and particles having sizes smaller than about 5 to 30 microns; 
 (h) passing the filtrate from the second filter through a first filtration apparatus, wherein the first filtration apparatus is an ultrafiltration apparatus which retains all or substantially all of the remaining humin and humic acid molecules while allowing the solution comprising the solubilized fulvic acid molecules to pass through; 
 (i) passing the filtrate from the first filtration apparatus through a second filtration apparatus, wherein the second filtration apparatus is an ultrafiltration apparatus or a nanofiltration apparatus, and wherein the second filtration apparatus retains all or substantially all of the fulvic acid molecules while allowing at least part of the water to pass through. 
 
     
     
       53. A method for extracting molecules of fulvic acid from a humus material comprising molecules of humin, humic acid and fulvic acid, the method comprising:
 (a) mixing ground humus material with water to solubilize at least some of the fulvic acid molecules; 
 (b) contacting microorganisms with the mixture in the presence of oxygen to oxidize any unoxidized organic compounds in the humus material; 
 (c) filtering the mixture through a first filtration apparatus, wherein the first filtration apparatus retains the humin molecules and at least some of the humic acid molecules while allowing the solubilized fulvic acid molecules to pass through the first filtration apparatus, wherein the first filtration apparatus is configured to retain particles or molecules having a molecular weight of more than about 12,500 Daltons; 
 (d) adjusting the pH of the mixture to about 5 to 8; 
 (e) adding a phosphate to the mixture to precipitate any iron and any aluminum in the humus material as iron phosphate and aluminum phosphate; 
 (f) removing any precipitated iron phosphate and aluminum phosphate from the mixture; 
 (g) filtering the mixture through a second filtration apparatus to separate at least some of the fulvic acid molecules from at least some of the humic acid molecules, wherein the second filtration apparatus is configured to retain particles or molecules having a molecular weight of about 2500 to 12,500 Daltons; and 
 (h) filtering the mixture through a third filtration apparatus, wherein the third filtration apparatus retains all or substantially all of the fulvic acid molecules which passed through the second filtration apparatus while allowing at least part of the water to pass through, wherein the third filtration apparatus is configured to retain particles or molecules having a molecular weight of about 250 to 1000 Daltons.